The earliest walking robots, built over a decade ago, were the Odetics family of walkers, which used insect-like legs. An early frame walker was the Martin Marietta (now Martin Lockheed) beam walker, which was designed for NASA in 1988 in response to the Mars Rover Sample Return mission. This robot had seven legs driven by ball screws. Three of the legs were on a large, outer frame, and four on a smaller inner frame.
The next frame walker of importance was the Dante robot (both Dante I and Dante II), design at Carnegie-Mellon University (CMU), which had eight non-orthogonal legs, four on each frame. Dante was a large vehicle, in excess of 900 pounds, and was not fully self-contained. The majority of the computing and all of the power sources were off-board. Another CMU frame walker is Daedalus, which was designed as an earth-based prototype of a lunar exploration vehicle. Daedalus is in the form of a hexagon, about 50 inches across and 80 inches tall, and weighs about 450 pounds. This robot was designed to be completely self-contained and employed rack-and-pinion orthogonal legs. Other frame walkers have been built, primarily as student experiments, and others have been proposed, but heretofore none have offered more than one primary means of locomotion.